The sequential events of neoplastic transformation of glial is being studied by light, electromicroscopic and autoradiographic methods in order to determine the cellulr source of gliomas in an in vivo experimental brain tumor model. Dogs and rats are inoculated intracerebrally with 0.01 ml of Avian Sarcoma virus (5 x 10 to the ninth power virus particles/ml). Experimental animals and their controls (inoculated with Avian myleoblastosis virus) are sacrificed at intervals from 5 minutes to 4 weeks after inoculation to assess the strucutral aspects of tumorigenesis, and the relationship of cells of the subependymal plate to those of the resultant gliomas. BIBLIOGRAPHIC REFERENCES: Vick, N.A., Bigner, d.d. and Lin, J.: Glial tumorigenesis: The role of the subependymal plate. J. Neuropath. Exp. Neurol: 35, 359, 1976. Vick. N.A. Grinker's Neurology, 7th Edition, Charles C. thomas Publisher, Springfield, Illinois, 1976. @DTX* 1NS-12584-2*